As a control method for a press apparatus and a workpiece transfer apparatus in a tandem press line, a phase difference control method is conventionally known. In this phase difference control method, the die position, that is, the press angle of a press apparatus on the upstream side of the tandem press line and that of a press apparatus on the down stream side of the tandem press line are controlled to have a predetermined phase difference so that a workpiece transfer apparatus does not interfere with the dies when carrying in and carrying out a workpiece. Such a phase difference control method can transfer a workpiece without stopping the upstream side press apparatus and the downstream side press apparatus, and allows a single workpiece transfer apparatus to smoothly transfer a workpiece between the aforementioned press apparatuses without interfering with the dies. Therefore, it has advantages in that productivity is high and apparatus costs are low.
For example, a technique relating to a control method using a phase difference control method as described above is disclosed in Japanese Unexamined Patent Application, First Publication No. 2004-195485. This technique controls a workpiece transfer apparatus synchronously with the press angle of an upstream side press apparatus in a die interference zone when the workpiece is carried out from the upstream side press apparatus, and controls the workpiece transfer apparatus synchronously with the press angle of a downstream side press apparatus in a die interference zone when the workpiece is carried in to the downstream side press apparatus. Furthermore, it controls the workpiece transfer apparatus based on a control signal outputted from predetermined signal generation device in transfer zones other than the aforementioned die interference zones. Since such a signal generation device for controlling the transfer zones is provided, the workpiece transfer apparatus can be operated even when the upstream side press apparatus and/or the downstream side press apparatus are stopped. Therefore, it is possible to improve the production efficiency.
Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2004-195485